This invention relates to coupling an electro-optical device to an optical fiber splitter and more particularly, an arrangement which provides significantly reduced coupling losses and improved uniformity of the light power supplied to the optical fibers.
As is well known in the optical fiber field, it is desirable to couple optical fibers to electro-optical devices with a minimum loss of optical power. This objective has been the source of an extensive amount of research. Additionally, many attempts have been made to provide low loss fiber-to-fiber connections. Typically, the ends of the fibers to be connected are placed in close proximity. In this manner only a small amount of optical power is lost. A large number of methods and devices have been developed to facilitate the alignment of one optical fiber with another and to facilitate the mechanical connection of one fiber with another once they have been aligned. Additionally, a number of connectors are known which provide precision alignment of one fiber with another as the connector is secured around the fibers. These known aligning and connecting techniques have been primarily related to the connection of one fiber to another, whether as a single fiber connector or as discrete components of a cable connector.
It is occasionally necessary to connect a single optical fiber to a plurality of optical fibers. A device providing such a connection is commonly referred to as a splitter. Connections of this type present a substantially different set of problems than are encountered in the end-on connection of two single fibers. As is well known, an optical fiber generally consists of a core region where transmitted light is concentrated and a surrounding layer of a cladding material. In order to obtain optimum light transmission from one fiber to another, the core regions of the two fibers are placed in precision end-on alignment. This task is complicated when more than one fiber must be aligned with a single core region. One approach suggested in U.S. Pat. No. 4,083,625 involves scraping the cladding from the edges of the fibers which are to be adjacent one another. The core is then partially removed so that each fiber contributes a portion of the total core area. In one embodiment, the total core area of the fibers on one side of the splice equals the core area of a single fiber on the other side of the splice. Another splicing technique calls for the removal of the cladding from the end regions of the fibers being spliced. This provides a high ratio of core area to total cross section in the fiber bundle. This permits a greater portion of the light incident on the fiber bundle to enter the light transmitting core regions.
In a typical arrangement for providing a splice between a plurality of optical fibers and an electro-optical device such as for instance an LED, the plurality of fibers are spliced to a single fiber and this fiber is coupled to the LED. A variety of arrangements for coupling a fiber to an electro-optical device and the difficulties encountered in obtaining a minimum loss of optical power in such connections are described in U.S. Pat. No. 4,065,203. As may be appreciated, the complexity and loss of optical power associated with conventional electro-optical device to optical fiber splitter arrangements are undesirable.